1. Field of the Invention
The present invention relates to a wet type friction contact device which may be applied to a clutch and a brake of a vehicle and an industrial machine.
2. Description of the Related Art
As an example of a wet type friction contact device, in a wet type clutch which is used in an automatic transmission of a vehicle: a plurality of flywheels as driving members are connected to a crankshaft of an engine; and a plurality of clutch plates are faced movably to these flywheels. A friction member (clutch facing) as a non-driving member is stuck on each of clutch plates; and clutch plate is constructed so as to be pressed to the flywheel side by a pressure plate. Also, lubricating oil as fluid intervenes between the flywheel and the clutch plate. In this wet type clutch, by the friction force of the contact surface between the friction member (non-riving member) and the flywheel (driving member) as the mating member, the driving force of the flywheel is transmitted to the torque converter side.
On the other hand, as an example of a dry type friction contact device, in a disc brake which is used in a vehicle: a disc as a driving member is rotated integrally with wheels; and a pad is faced movably to this disc. A friction member (brake lining) is stuck on this pad, and the pad is constructed so as to be pressed to the disc side by a caliper and so on. In this disc brake, braking of the disc is conducted by friction force of the contact surface between friction member (non-driving member) and the disc (driving member) as the mating member. In the same way as that in the above, also in a drum brake, braking of a drum is conducted by friction force of the contact surface between the drum and and the friction member (brake lining) which is stuck on the shoe. Also, in a general dry type clutch, a flywheel as a driving member is connected to a crank shaft of an engine, and a clutch plate is faced movably to this flywheel. On this clutch plated, a friction member (clutch facing) is stuck as a non-driving member, and the clutch plate is constructed so as to be pressed to the flywheel side by a pressure plate. In this dry type clutch, a driving force of the flywheel is transmitted by the friction force of the contact surface between the friction member (non-driving member) and the flywheel (driving member) as the mating member.
The conventional wet type friction contact device is superior in wear resistance and almost does not need the exchange thereof by the cooling effect of the fluid of lubricating oil, but the conventional wet type friction contact device has the following disadvantages. As shown in FIG. 2, the coefficient of dynamic friction .mu. of the paper material to steel as the mating member is 0.14, which is the highest coefficent of dynamic friction as compared with those of the existing material such as a graphite resin material, cork material, sintered alloy material and semi-metallic material. So the coefficient of dynamic friction .mu. of those existing material to steel as the mating member ranges from 0.05 to 0.14 and it is relatively low. This is because contact ratio between solid bodies is reduced owing to intervening of lubricating oil as fluid at each of contact surfaces between friction member as non-driving member and the driving member thereof as the mating member. Accordingly, in order to secure a large amount of torque capacity, as the conventional wet type friction contact device, it is necessary to multiply driving member and non-driving member and enlarge diameter thereof so that the unit thereof is necessary to be large-sized. For example, in the case of the wet type clutch, the fact is that multi-disc of flywheel and so as mentioned above brings about the large-sized clutch unit. Accordingly, in an automatic transmission and a differential limiting-device of a passenger car, the above-mentioned disadvantages cause a large amount of difficulty in realizing high performance, small size and lightness in weight.
On the other hand, in the case of the conventional dry type friction contact device whose contact ratio between solid bodies is relatively large, the coefficient of dynamic friction u of the friction member to steel as the mating member ranges from 0.3 to 0.5 and amounts are relatively high level. Accordingly, it is possible to secure relatively a large amount of torque capacity, however, there is no effect of cooling by the fluid of lubricating oil and so on. Therefore, the conventional device has the following disadvantages: wear resistance is inferior caused by temperature rise on each of contact surfaces; and disassembly and exchange of the friction member is necessary.